Optical Density:

Read the optical density of your sample at a wavelength of 600 nm (O.D.600). To do this:

  1. Let the spectrophotometer (opposite) "warm up" for at least 15 minutes so you get the correct reading.

  2. Adjust the wavelength to 600nm (green light). (Why 600nm?)

  3. Place a cuvette containing a blank of medium (L-broth) in the machine and adjust so the reading is zero.

  4. Place a cuvette containing your sample in the machine and read the optical density (O.D.).

N.B. You can only accurately read OD up to a value of about 2.0. Above this level readings are not accurate. If the reading from your sample is higher than 2.0, make a 10-fold dilution (as before) and record the OD of this. (Don't forget to multiply the reading by 10 to take account of the dilution).

Look at your results

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